A Factor IX Gene Therapy Study (FIX-GT)

Severe haemophilia B (HB) is a bleeding disorder where a protein made by the body to help make blood clot is either partly or completely missing. This protein is called a clotting factor; with severe haemophilia B, levels of clotting factor IX (FIX) (nine) are very low and affected individuals can suffer life threatening bleeding episodes. HB mainly affects boys and men (normally one in every 30,000 males). Current treatment for HB involves intravenous infusions of factor IX as regular treatment (Prophylaxis) or 'on demand'. On demand treatment is highly effective at stopping bleeding but cannot fully reverse long-term damage that follows after a bleed. Regular treatment can prevent bleeding, however can be invasive for patients and also expensive. This research study aims to test the safety and effectiveness of a gene therapy which produces Factor IX protein in the body. The gene will be given using an inactivated virus called "the vector" ( FLT180a), in a single infusion. The vector has been developed from a virus known as an adeno- associated virus, that has been changed so that it is unable to cause a viral infection in humans. This "inactivated" virus is further altered to carry the Factor IX gene and to make its way within liver cells where Factor IX protein is normally made. Up to three different doses cohorts of FLT180a will be tested, in up to 24 patients with severe haemophilia B. Patients will be recruited from haemophilia centres in the EU and US. Patients will be in the trial for approximately 40 weeks and will undergo procedures including physical examinations, bloods tests, ECGs and liver ultrasounds.